Open ocean communities

The open waters of the oceans are all impacted by solid waste, sediments, nutrients and toxic pollutants. Many of these have an impact at the base of the food chain, with nutrients and sediments both affecting productivity and species dominance in the phytoplankton, and thereby affect the high levels of grazers and predators. Toxins are also generally absorbed at lower levels in the food chain, but become concentrated at higher levels.

Solid waste is often more of an issue for higher levels of the food chain and can be a particular problem for certain species such as turtles . There is also growing evidence that solid waste is being used, in a process of rafting, by benthic or coastal species and is supporting the introduction of alien species (q.v.?) to new areas.

Climate change is already beginning to warm the surface waters of the oceans and there is some evidence that patterns of surface currents may be varying. One direct impact could be the simple shifting of populations to match the changing conditions. Studies off the coast of California in the USA have looked at changing conditions in this area and shown both increasing temperatures and a decline in zooplankton biomass. These changes, which clearly provide an example of the types of changes that will be common more widespread as climate change continues, have led to an overall diminution of seabird numbers, large declines of cold-water species, and smaller increases in warm-water species.